How to make a GE ExII UHF Receiver work at 425Mhz

Three items need to be addressed :

          1.Helical front end [ L301, L302, L303, L304, L305 ] needs more inductance. Open the bottom of the front - end and get out the American Beauty [150W] and unsolder  the 5 coils.  Using  #10 solid copper, make a 1/3 turn coil to match  the coils that were taken out. Take off the enamel on the end of the original coil and solder (gun) the 2 coils together. After soldering the coils into the chassis , be sure to align the coils (by bending).

                2. Next is the  oscillator / multiplier that needs a lot of work!  Pull the oscillator board out as it is easier to work on. Solder a wire from H7 / F1 / brn wire to ground. Pull the brn wire  off the board. This is  F1  crystal ground.  Unsolder white wire at H3 and fold it back with a tie. Make a jumper and short the 10v  trace (red)  to where the white wire (rx osc control) was attached.  Add a 2-4 pf cap across C407. Run a 7” wire from H6 / blue wire / compensation line to P903, pin 5. A FB slipped over pin 5 is great. On this wire install a ferrite bead - (low freq. type).  Install 2-chip caps (.001 - .01uF )  near  channel element on the 10v line and the compensation line to ground. Disc caps – OK. Install another chip (.001) at R419 to ground. Install a .01 chip cap on the channel element – pin  4 to gnd. The compensation line really radiates RF.

                3. Next is the preamp .  Install a 10uF Tant. Cap across C2308. Install a .001uF chip cap across C2307.  Unsolder the metal shield on L2301. Solder a small solid wire (resistor wire) at the top of the where it is folded over and will form an X    -capacity hat.

For Reliability: 

                      Resolder : crystal –ch. ele. , 6 pins on ch. Ele. , 6 pins ch. Ele. on osc board

                                              7 pins, J602 and 7 pins P903 / IF DET. Board.

                          Stabilant :  6 pins / ch. ele. ,  7pins / J602 , 7 pins / P903 ,  5 screws on  preselector ( L301 – L305 ) ,  3 screws  ( L306 – L308 ) osc / mult. 

Info:

Osc / mult board  @ 425 mhz,  Hi side inj.     Xtal = op. freq.+ 11.2 / 27

                             L401  3X     48.46 mhz

                             L402  3X    145.4 mhz

                             L407  3X    436.2 mhz

Compensation range : -10 to 50 degrees C ……..3.7v  to 4.3v

****** For best  ( lowest) distortion*******  

Always pick the IF det. Board that has the adjustable IF cans and not the fixed inductor boards. These boards let almost 4 ¼  Khz dev. pass verses about 3 Khz for the fixed inductor.

………………………………………………………………………………………………………………